Datasheet

Chapter 2
Electrical and optical properties
This chapter discusses electrical properties of pulsed and CW QC lasers for special
issues concerning CW operation, see Chapter 4, (CW mode), p.16.
2.1 Electrical limits
2.1.1 What is the maximum allowed duty cycle?
This strongly depends on the laser.
As a general rule, most lasers sold by Alpes Lasers SA are capable of being driven
up to 10% duty cycle with pulse lengths up to 100ns. Whenever you drive a laser at
a duty cycle higher than specified, monitor the average output power; do not increase
the duty cycle any more when the power saturates, but reduce it again to stay on the
safe side.
If possible, increase the duty cycle by reducing the pulse period, not by increasing
the pulse length, since the latter is more dangerous: It increases the short time heat
load on the laser, instead of the average heat load.
Before doing such experiments, it is recommended to contact Alpes Lasers
SA, otherwise the responsibility is with you!
2.1.2 What happens if I increase the duty cycle?
You will see no decrease of the maximum instantaneous power of the device up to
2..5% depending on the device. Around 5..20%, the maximum average power will be
obtained. Over this limit, the increase of average power due to increase of duty cycle
will be smaller than its decrease due to increased threshold current (caused by higher
average temperature of the structure).
The precise percentages depend both on the technology used (normal pulsed 2
mW or high power DFB) and the wavelength. For normal pulsed devices at short
wavelength (4..5um), the maximum duty cycle is 3..5%, and at longer wavelength it
may go up to 8% or even 20% for high power DFBs.
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